In Woody Allen's 1998 movie Celebrity, many people thought that Leonardo DiCaprio's cameo was the best thing in it. DiCaprio played a spoiled celebrity, high on self gratification and over-indulgence. DiCaprio's Generic Celebrity bullied girlfriends, trashed hotel rooms, and offered around leftover groupies as if they were stale sandwiches. Like I said, most people enjoyed DiCaprio's over-the-top self-lampooning performance in Celebrity. Others might have wondered if they watching DiCaprio: A Documentary.

Leonardo DiCaprio is back, and everyone is doing the maths. It's been six years since the blockbuster Titanic, three years since his last movie The Beach. Three years is a dangerously long career hiatus for any actor, but at least DiCaprio is coming back with style, with starring roles in two major movies with two A-list directors released within a fortnight of each other. Martin Scorsese's beleaguered Gangs of New York, and Catch Me If You Can, Steven Spielberg's comedy about real life con artist Frank Abagnale.

This week, DiCaprio was in Leicester Square for the former's UK premiere, the only one not shivering in the freezing cold because he had 2,000 screaming friends to keep him warm. Nobody mentioned it at the time, but some of those fans might have been screaming in horror. Who was this impostor? Where was baby-faced Leo, the dimpled Romeo of a thousand schoolgirl bedroom walls? DiCaprio, now 28, looked larger, older, broader, slightly wispy of chin, stronger, more serious. Had the blue-eyed boy wonder done the teen-unthinkable: Had he become a man?

Leonardo Wilhelm DiCaprio was born in Hollywood on 11 November 1974. It is said that he was named after he'd kicked inside the womb when his parents were staring at a Leonardo da Vinci painting. (True or not, this is just the kind of detail that young Titanic fans lapped up.) DiCaprio's first feature, 1991's Critters 3, was followed a couple of years later by This Boy's Life, where he played opposite Robert De Niro. The same year, his performance as a retarded boy in What's Eating Gilbert Grape? won him an Oscar nomination. However, it was when DiCaprio took the lead role in Baz Luhrmann's Romeo and Juliet in 1996 that the teen grapevine really started humming.

The following year, Titanic was released. Industry opinion was that it had cost too much, taken too long to make, and was unlikely to do great box office. It went on to become one of the highest grossing movies of all time. Young girls would vie with each to see who could watch DiCaprio sink to his death beneath the inky waves the most times (the record was 400). At a Paris airport, a girl attached herself to DiCaprio's leg, digging her fingernails in so hard it took two security guards to get her off. It was the beginning of what DiCaprio's Catch Me If You Can co-star, Tom Hanks, recently referred to as DiCaprio's 'Post-Titanic Stress Syndrome'. It was 1997. DiCaprio was 23 years old.

DiCaprio has since described the period following Titanic as 'empty'. 'There's no handbook. I couldn't go to Barnes & Noble and pick up a book on what it was like: A Guide To Being Famous For Dummies.' Maybe the lack of this useful tome explains DiCaprio's subsequent über-party animal behaviour. More likely, he just wanted to have fun. The media certainly had fun with the increasingly pudgy DiCaprio, faithfully recording his expanding waistline, and brawling-wenching behaviour, alongside his friends, Tobey Maguire, Lukas Haas, magician David Blaine, and celebrity accountant Dana Giacchetto.

There was another side to DiCaprio, that of the keen environmentalist, who once popped up on the ABC channel interviewing Bill Clinton. However, this more thoughtful side was all but eclipsed by DiCaprio's quasi-decadent behaviour. He and his friends mooched around together like a Mickey Mouse rat pack, at one point dubbing themselves 'The Pussy Posse' (something DiCaprio vigorously denies). After he paid Demi Moore too much attention, her then-husband, Bruce Willis, away on set, quipped: 'He'll be Leonardo DeCapitated when I get home.'

Where his career was concerned, it was more a case of Leonardo DeActivated. Post-Titanic, DiCaprio turned down Star Wars, American Psycho and Spider-Man. Among the movies he did make, The Man In The Iron Mask and The Beach (for which he got $20 million) were flops. Meanwhile, his relationship with Brazilian model Gisele Bundchen faltered, while friend Giacchetto was arrested for stealing millions of dollars from clients, including DiCaprio. It was a wake-up call that marked the beginning of the career hiatus, now broken by Catch Me If You Can and Gangs of New York (which DiCaprio itched to do since he first heard of the project at 16).

Not that DiCaprio was a reformed character. During Gangs..., he pelted paparazzi with horse muck, was allegedly ticked off by Scorsese for partying too hard, and co-star Daniel Day-Lewis moved out of his hotel, weary of the mayhem caused by DiCaprio's entourage.

So where does DiCaprio sit now? The answer appropriately enough is very prettily indeed. As it happens, DiCaprio's performance in Gangs of New York is so-so, all but eclipsed by the full-wattage Oscar-chasing Day-Lewis as Bill The Butcher. Saying that, it doesn't hurt at all to have a comeback (at the grand old age of 28) where both Martin Scorsese and Steven Spielberg are jostling each other to hail you as the best actor of your generation. Of projects lined up for the future, DiCaprio is slated to be back working with Scorsese on Aviator, a biopic of the early life of Howard Hughes, and also back with Baz Luhrmann, playing the lead in Alexander the Great. All in all, DiCaprio is pretty much where he always wanted to be, and might have been much earlier, had his credibility not been washed away by the success of Titanic.

This is the eternal conundrum of Leonardo DiCaprio. Titanic made his present but to an extent it also screwed his future. Many people don't see that DiCaprio has any appeal: to them, he's just another pretty boy actor with floppy hair and delusions of greatness, the River Phoenix who didn't die, the Keanu Reeves who can remember lines. Others, including many stellar directors, believe that DiCaprio has something special to offer. So, crucially, does DiCaprio. He is the sort of actor who sits proudly in his production office in front of signed posters of Scorsese's Raging Bull and Mean Streets. Indeed, we forget now, but despite the girly face, with early movies such as This Boy's Life and What's Eating Gilbert Grape?, DiCaprio seemed set to become an edgy character actor, along the lines of a De Niro or a Pacino, or more latterly a Benicio Del Toro or Ed Norton.

However, these actors, actors DiCaprio admires, would never have convinced as fluffy romantic leads like DiCaprio did in Titanic. If they were musicians, they would be edgy rock stars. By contrast, when Titanic happened DiCaprio suddenly found himself having to run his career like some cheesy one-man boy band. Donny Osmond instead of Iggy Pop. Milking his teen appeal for all that it was worth, watching his credibility turn to cheese.

DiCaprio has gone on record saying that as far as he is concerned from now on the heat is off: 'My celebrity will never get bigger than post-Titanic. That'll never happen, so I don't give a crap what people think.' Then again, lessons have been learned, right? DiCaprio is no longer Generic Celebrity to the point where people couldn't work out where the real DiCaprio ended and the fake one began in his Woody Allen cameo. Well, put it this way: in a recent interview in Australia, it was pointed out to DiCaprio that his next two roles, Hughes and Alexander, are both Icarus figures. DiCaprio fell silent and the world waited for his thoughts on those mere mortals so vain and reckless they fly too close to the sun and end up falling to their deaths - a metaphor for high-octane celebrity if ever there was one. DiCaprio's answer, when it came, was brief and to the point: 'Fuck Icarus.'

LEONARDO DICAPRIO

DoB: 11 November 1974 (Echo Park, Los Angeles)

Height: 5 foot 11in

Film debut: Critters 3 (1991)

Current films: Martin Scorcese's Gangs of New York (with Daniel Day-Lewis and Liam Neeson); Steven Spielberg's Catch Me If You Can (with Tom Hanks)